The present invention relates to a bottom tension boom having excellent wave compliance with regard to any individual flotation unit in that its individual flotation members freely move with the wave, thereby minimizing relative velocity between the water in the wave and the flotation member. Thus, a compliant boom is capable of extensive movement, with regard to any upward or downward motion, any forward or backward motion, and any lateral motion caused by waves.
Heretofore, booms, such as those towed by boats and employed for the containment of floating matter such as oil upon a sea, have contained therein a top and, sometimes, a bottom tension member. The top tension cable is generally connected to a flotation member which in turn is generally connected to an impervious skirt. An open-strap system extends downwardly from and, if a bottom tension member is utilized, connects the skirt with said bottom member. All components of such an apparatus are of the same length. Naturally, with the top tension member being under tension, wave compliance is very poor in that the individual flotation members are not freely permitted to bob up or down, laterally, or backward and forward.
One such device is set forth in U.S. Pat. No. 3,852,965 which has a top cable 15, a flotation member 20, a pendant skirt 25, an open-strap network 26, and a bottom tension cable 16. Moreover, straps 26 are attached solely in a vertical position, and such structure further limits any wave compliance since the straps are relatively non-extendible.
A bottom tension boom is discussed in Proceedings of Joint Conference on Prevention and Control of Oil Spills, Mar. 13-15, 1973, Washington, D.C. However, such a boom is still unsuitable to produce wave compliance due largely to the utilization of a lattice having vertical straps. That is, the vertical nature of the lattice prevents upward or downward bobbing of the individual buoyancy units. Moreover, the length of the skirt is equal to the length of the bottom tension line which is attached, thus abating any good wave compliance of the buoyancy units.
Other prior art materials relating to flotation booms which have poor wave compliance are U.S. Pat. No. 2,693,161 to Stubbs, U.S. Pat. No. 3,648,463 to Ayres, U.S. Pat. No. 3,740,995 to Fossberg, U.S. Pat. No. 3,903,701 to Gauch, Canadian Pat. No. 906,772 to Fossberg, and French Pat. No. 2,009,655 to Henke.